This invention relates to an apparatus and method for fatigue testing a vehicle wheel, such as is required of high performance racing wheels
Fatigue testing of vehicle wheels is frequently performed by wheel manufacturers to ascertain the number of revolutions the wheel can withstand before failing when a predetermined moment is applied to the wheel. Many of the organizations which govern a particular type of racing set standards for fatigue testing which must be met by a manufacturer's wheels before they can be used in that type of racing.
In the past, machines for fatigue testing vehicle wheels have simulated the action of the wheel on the vehicle. The wheel is mounted to a plate and a predetermined moment is exerted on the plate through a shaft mounted to the plate. The wheel is then spun about an axis coincident with the longitudinal axis of the shaft, which replicates stresses experienced by a wheel as mounted to a vehicle during operation of the vehicle.
The present invention provides an apparatus and method for fatigue testing a vehicle wheel, which also simulates the stresses experienced by a wheel as mounted to a vehicle. In direct contrast to the known testing procedure and apparatus, however, the present invention maintains the wheel stationary during testing. This allows the wheel to be observed and monitored during the test, which may reveal to the manufacturer certain areas of weakness in the wheel not detectable during a test in which the wheel is spun.
In accordance with the invention, an apparatus for fatigue testing a vehicle wheel comprises wheel support means for maintaining the wheel stationary, and fatigue stress inducing means connected to the wheel for inducing stress in the wheel so as to simulate stress induced in the wheel when the wheel is mounted to a vehicle. The wheel support means preferably comprises a wheel supporting plate member to which the wheel is clamped. The fatigue stress inducing means comprises a stress plate to which the wheel is bolted by means of bolt-receiving openings provided in the wheel, and a non-rotatable shaft extending from and interconnected with the stress plate. At least a portion of the shaft is mounted to a lateral loading assembly, which is rotatable relative to the shaft. The lateral loading assembly exerts a force on the shaft in a direction other than in line with the longitudinal axis of the shaft, and preferably in a direction substantially perpendicular thereto. In a preferred embodiment, the lateral loading assembly comprises a bearing member into which at least a portion of the shaft extends, lateral loading means exerting a lateral force on the bearing member which causes the bearing member to move laterally relative to the shaft, and means for imparting rotation to the bearing member when the lateral force is exerted on the bearing member. When the lateral force is exerted on the shaft and the lateral loading assembly is rotated, the shaft is caused to "wobble", which action is transferred through the shaft to the stress plate. Wobbling of the stress plate simulates the relationship of the wheel to a vehicle when the wheel is mounted to the vehicle and the vehicle is operated. The lateral force on the shaft is continuously exerted while the lateral loading assembly rotates so that, in time, the wheel fails due to fatigue loading. Based on the number of revolutions of the lateral loading assembly, the wheel manufacturer can determine whether the wheel conforms to the desired standards.
In a preferred embodiment, the lateral loading assembly comprises a bearing member mounted for slidable lateral movement within a carriage assembly. The carriage assembly is connected to the rotation imparting means for rotating the bearing member. A fluid-operated cylinder assembly is mounted to the carriage assembly, which is operable to selectively exert a lateral force on the bearing assembly. The exertion of a lateral force on the bearing assembly causes the bearing assembly to slide laterally within the carriage assembly, and to laterally deflect the portion of the shaft connected to the bearing assembly due to yielding of the wheel. In a particularly satisfactory construction, fluid pressure is supplied to the fluid-operated cylinder assembly through an internal passage provided in a shaft to which the carriage assembly is connected. A motor or the like is connected to the shaft for imparting rotation thereto, which is transferred through the shaft to the carriage assembly. A conduit extends between the shaft adjacent the carriage assembly and the fluid-operated cylinder for supplying fluid pressure to the cylinder.
Disabling means is preferably provided for disabling the apparatus when a predetermined amount of deflection of the shaft occurs, which corresponds to failure of the wheel.
The invention also contemplates a method of fatigue testing a wheel, substantially in accordance with the foregoing description.